Alkali-soluble cellulose acetate textile material and process for producing same



United States Patent O 3,425,788 ALKALI-SOLUBLE CELLULOSE ACETATE TEXTILE MATERIAL AND PROCESS FOR PRODUCING SAME Victor B. Holland, Merton C. Propst, Jr., and Harold W. Wyatt, Kannapolis, N.C., assignors to Cannon Mills Company, a corporation of North Carolina a No Drawing. Filed Oct. 8, 1964, Ser. No. 402,642 US. Cl. 8-129 4 Claims Int. Cl. D06m 11/02- ABSTRACT OF THE DISCLOSURE Alkali-soluble cellulose acetate textile is produced by treatment of said textile with an aqueous solution containing chromic acid, or a dichromate such as sodium dichromate, and an acid such as nitric, sulfuric or oxalic acid.

acid, such as nitric or sulfuric acid. Certain organic acids,

e.g. oxalic acid, may be used instead of the inorganic acid.

The new alkali-soluble cellulose acetate textile material of this invention may be in any of the usual textile forms such as fiber, yarn or fabric, and it may be combined with other textile materials by fiber blending, yarn spinning or knitting or weaving in a textile fabric. The alkali-soluble component of such textile products may be easily and quickly removed by treating the textile material containing the alkali-soluble component with a dilute alkaline solution such as for example a 0.01% to 3% sodium hydroxide solution. This dissolving solution also may be in the form of boiling solutions of mild alkalis or soap solutions commonly employed for washing textile materials in textile mills.

In the usual case, the solubility of the treated cellulose acetate material will be substantialy complete, i.e. 98% to 100% soluble. For some purposes, a lower solubility, such as 90% to 95%, might be used, and where desired it can be obtained by use of less concentrated treating chemicals, i.e. the dichromate and acid, or by employing a shorter period of time, or a lower processing temperature. The general ranges for the treating conditions necessary to provide a solubility of 90% to 100% are as follows:

Concentration of dichromate-0.3% to 4% which is equivalent to about 0.23% to about 3.1% by weight of chromic acid Concentration of nitric acid1% to about 18%.

Temperature rangeRoom temperature, 80 R, up to Time1 minute to about 125 minutes The cellulose acetate material that is treated and rendered alkali-soluble in accordance with the present invention, may be the regular cellulose diacetate or the more recent cellulose triacetate.

The treated cellulose acetate textile material has substantially the same textile properties as it had before treatment and may be used as a textile material and processed in the same way as the original cellulose acetate. The loss of breaking strength, of the cellulose acetate, depends on ice the degree of solubility desired. If the solvent is to be .5 (or more) sodium hydroxide, the treatment conditions and chemical concentrations can be such that the breaking strength is reduced about 22-25%, and the weight loss is minor. More importantly, we have found that the yield point of the treated cellulose acetate is only about 4% lower than that of the untreated cellulose acetate. This does not necessitate any change in the usual textile manufacturing processes in which the cellulose acetate material is used. To make the cellulose acetate soluble in mild alkalis, treatment must be more drastic and strength loss is about 50%.

An illustrative but non-limiting example of the process of treating the cellulose acetate textile material to render it alkali-soluble in accordance with our invention, and the properties of the treated product, are as follows:

PROCEDURE FOR TREATMENT Wash the cellulose acetate in hot water containing a suitable free-rinsing surface-active agent. Rinse.

Make up the reagent solution. Bring the solution to the desired temperature. Place the cellulose acetate in the solution. Keep the solution at a constant temperature. Agitate from time to time. Remove the cellulose acetate, wash it thoroughly in hot water, and dry it.

CONDITIONS OF TREATMENT Specimens-Cloth Ratio, liquid to fiber20: 1

Temperature-470 F.

Formula-0.8% sodium dichromate -i2H O; 2.4% nitric acid, as

Determination of solubility in alkalis: Adjust temperature of solution to 100 F. Immerse the cellulose acetate specimen, bring to a boil. Boil 5 minutes. Pour through a stainless steel screen, 150 x mesh. Rinse residue until alkali-free.

A high degree of alkali-solubility can be obtained even though the time and temperature are changed considerably. If a lower treatment temperature is used, the time must be increased, as must also the concentration of reagents.

Lower temperature seems to favor higher strength retention and less weight loss of the cellulose acetate.

One of the commercially important uses of the alkalisoluble cellulose acetate of this invention is the production of non-puckering fabrics as disclosed in Holland and Propst Patent 3,169,557, issued Feb. 16, 1965. As disclosed more in detail in that patent, differences on contraction of adjacent portions of fabrics, such as for example the main body portion and the decorative border portion, respectively, of a water absorptive towel, may be avoided by using a special type of yarn in the border portion. This yarn is purposely spiraled or coiled to provide excess length which becomes useful and effective upon wetting of the yarns and straightening out of the coils or spirals. To enable the coiled or spiraled yarn, usually the filling yarn in the woven fabric, to be woven satisfactorily in the decorative border using conventional weaving equipment, a temporary core yarn is employed, around which the filling yarn is coiled or spiraled, the core yarn acting as a carrying medium for the spiraled or coiled yarn. It is necessary for this core yarn to be easily removed and preferably by the use of liquids or solutions commonly employed in towel or fabric finishing. One of the important commercial advantages of the cellulose acetate yarn of the present invention is that it is relatively inexpensive and is a readily available commodity in fiber, yarn or fabric form, and its processing in accordance with the present invention to render it alkali-soluble, is a relatively inexpensive process,

It is to be understood that the alkali-soluble textile material of the present invention is not limited to the above mentioned example of special yarn, or its use, for example in lace manufacture wherein the alkali-soluble portion of the lace fabric would be removed by scouring or the like to produce the desired lace design.

It is also to be understood that various modifications and changes may be made in the above discussed materials, process conditions and resulting product without departing from the scope of the invention as defined in the appended claims.

We claim:

1. A process of producing alkali-soluble cellulose acetate textile material which comprises treating nonalkalisolu-ble cellulose acetate textile materialwith an aqueous solution containing about 0.23% to about 3.1% by weight of chromic acid and about 1% to 18% by weight of a strong acid selected from the group consisting of nitric and sulfuric under temperature conditions sufiicient to obtain a textile material that is at least 90% soluble in about 0.01% to about 3% aqueous alkali solution without appreciably aifecting the tensile strength of the material.

2. A process as defined in claim 1 wherein said treatment of the textile material is carried out at a temperature of from about room temperature to about 170 F.

3. An alkali-soluble cellulose acetate textile material produced by the process of claim 1.

References Cited UNITED STATES PATENTS 3/1947 Williams et al 8-130 5/ 1960 Reinhardt et a1 8129 X OTHER REFERENCES Reinhardt et al.: Industrial and Engineering Chemistry, January 1958, pp. 83-86.

Reinhardt et al.: Textile Research Journal, October 1959, pp. 802810.

DONALD LEVY, Primary Examiner.

H. WOLMAN, Assistant Examiner.

US. Cl. X.R. 

